Heat-exchanger module

ABSTRACT

In a heat exchanger unit with a plurality of tubes for the circulation of a first fluid and a inner sleeve for the circulation of a second fluid a transverse partition-wall is disposed between the outer shell and the inner sleeve assuming said circulations. Said transverse partition-wall delimits two annular spaces which communicate respectively with external ducts for the admission and discharge of the fluids. The ducts are immediately adjacent to said transverse partition-wall in order to avoid differential expansion under both steady state and transient flow conditions between the outer shell and the tubes of the heat exchanger unit.

United States Patent [191 Pouderoux et al.

[4 1 Dec. 17, 1974 HEAT-EXCHANGER MODULE [73] Assignee: Stein Industrie, Paris, France [22] Filed: Feb. 6, 1973 [21] Appl. No.: 330,114

Owen l65/l6l X Pouderoux 165/158 Primary Examiner-Charles J. Myhre Assistant Examiner-Theophil W. Streule, Jr. Attorney, Agent, or Firm-Cameron, Kerkam, Sutton, Stowell & Stowell [57] ABSTRACT In a heat exchanger unit with a plurality of tubes for the circulation of a first fluid and a inner sleeve for the circulation of a second fluid a transverse partition-wall is disposed between the outer shell and the inner sleeve assuming said circulations. Said transverse partition-wall delimits two annular spaces which communicate respectively with external ducts for the admission and discharge of the fluids. The ducts are immediately adjacent to said transverse partition-wall in order to avoid differential expansion under both steady state and transient flow conditions between the outer shell and the tubes of the heat exchanger unit.

6 Claims, 3 Drawing Figures HEAT-EXCHANGER MODULE The invention relates to heat exchanger units comprising a plurality of tubes for the circulation of a first fluid, said tubes being disposed in a bundle between two tube plates within an inner sleeve for the circulation of a second fluid, provision being made at least at one end of the tube bundle for a rectilineal portion followed by elbowed portions which constitute expansion bends for compensating differential expansions. These tubes are subdivided into two sets of equal number and disposed on two square lattices with a uniform pitch on each side of a principal lattice line along which the two lattices are relatively displaced by one-half pitch. The two lattices are placed in interjacent relation at the level ofthe expansion ben ds. At t his point and in the case of each lattice, the tubes of any given row which is perpendicular to the principal .line retain substantially the same cross-sectional area as in the rectilineal section and extend into the other lattice in such a manner as to form expansion bends in the plane of said row and to pass between the parallel rows of the tubes of the other lattice.

The present invention relates to improvements which are distinguished by the fact that the inner sleeve for the circulation of the second fluid delimits with the outer shell of the heat-exchanger unit and a transverse partition-wall two annular spaces consisting of an upper and lower space which communicate respectively with external ducts for the admission and discharge of the second fluid, said ducts being immediately adjacent to said partition-wall in order to admit of minimum differential expansion under both steadystate and transient flow conditions between said outer shell and the tubes of said bundle.

In accordance with a characteristic feature of the invention, the transverse partition-wall comprises a supporting ring fixed on the inner sleeve, two radial fins disposed on each side of the partition-wall within the annular spaces in order to prevent circulation of the second fluid in the vicinity of said partition-wall, with the result that the external ducts for the admission and discharge of the second fluid are insulated hydraulically and thermally both with respect to each other and with respect to said tube bundle.

In order to prevent thermal stresses on the outer shell, thermal insulation must be provided between the hot and cold portions of the annular spaces which are adjacent to the external ducts for the admission and discharge of the second fluid. To this end, a thermal screen is placed concentrically with and externally of the inner sleeve and extends along the annular spaces over a distance which is limited to a point located beyond the openings for the admission and discharge of the second fluid.

In order to facilitate the assembly operation, the ring for supporting the inner sleeve is fixed on an internal shoulder of the outer shell of the heat-exchanger unit.

In accordance with the invention, a plurality of heatexchanger units of the type described can be disposed at several locations in a steam generator circuit in order to carry out heating and vaporization of the water.

The following description relates to exemplified embodiments of the invention and is given with reference to the accompanying drawings, in which:

FIG. 1 is a vertical sectional view of a heat-exchanger unit in accordance with the invention;

FIG. 2 is a diagrammatic sectional view of the same unit in accordance with FIG. 1;

FIG. 3 shows a general layout of heat-exchanger units in accordance with the invention.

In FIGS. 1 and 2, each unit is essentially constituted by a shell 1 which is usually vertical and by a bundle of straight tubes 2 placed within said shelL'The ends of said tubes are welded respectively to a lower tube plate 4 and an upper tube plate 5 which are both placed within the shell 1 and located respectively at each end of this latter. Said tube plates are disposed in parallel on the circuit of a first heat-transfer fluid consisting in this instance of water in the form of either liquid or vapor. The second fluid consists of liquid sodium and circulates in contact with said tubes within the sleeve 12. In order to ensure systematic downward circulation, provision is made for one or a number of openings 15 for the admission of sodium at the upper end of the sleeve and openings 15a for the discharge of sodium at the lower end whilst the water flows within the tubes 2 in the upward direction from an inlet nozzle 8 to an outlet nozzle 9.

The annular chamber which is formed between the outer shell 1 and the inner sleeve 12 is separated by a partition-wall 20 in order to form an inlet space 21 and an outlet space 22 which may both be annular. The shell 1 is provided with sodium inlet and outlet nozzles 6 and 7 which open respectively into the spaces 21 and 22. In order to prevent spurious heat-transfer effects and thermal stresses which are liable to be detrimental to the good operation of the unit, a thermal screen is provided over part of the length of the spaces 21 and 22. In the example of construction shown in FIG. 1, said screen can be essentially composed of a jacket 23, the top end of which is welded to the sleeve 12 and the bottom end of which is free so as to permit of expansion, radial fins 24 which are fixed on the jacket 23, radial fins 25 which are fixed on the outer shell 1 and in which the stationary sodium is entrapped. The jacket 23 can contain either stationarysodium or any other material which forms a thermal screen.

The partition-wall 20 also serves to transmit the weight of the sleeve .12 and is composed of a ring 26, said ring being fixed on the jacket 23 and intended to rest on an annular flange 27 which is provided on the shell 1.

The presence of the annular chamber between the inner sleeve 12 and the shell 1 is turned to useful account for the assembly operations. The tube bundle which has been completely joined to the tube plates can be introduced into the outer shell together with the inner sleeve (the portion which is remote from the expansion bends being introduced at the top end).

The circulation of sodium with the two annular spaces reduces differential expansions between tubes and shell to a very appreciable extent both during steady-state operation and under conditions of transient flow. This would not be the case if the sodium were stationary within said space by reason of its thermal inertia.

In order to permit compensation for differential expansions during operation, the layout of each tube of the bundle forms an expansion bend 18 in the vicinity of one end of the unit, expecially at the topportion as shown in FIG. 1. The sleeve 12 which is provided around the tube bundle stops short of said expansion bends. Thus the expansion bends can occupy the entire available space within the chamber 11 which is provided for this purpose while at the same time enhancing the sodium flow at a distance from said expansion bends which are thus located in a calm zone and can be filled with neutral gas if necessary.

As shown in FIG. 2, the expansion bends can be arranged in a central bundle and .two outer bundles which make it possible to cancel the overall stress on the upper tube plate 5.

The heat-exchanger unit which is illustrated in FIGS. 1 and 2 is a separate assembly which is intended to be connected in series with other units in order to form a complete heat-exchanger (FIG. 3), for example a steam generator consisting of a heater-evaporator unit 29 and a superheater unit 30 in a liquid-metal flow circuit. The broken lines indicate the layout of the connecting piping in a conventional heat exchanger and the full lines indicate the layout which is made possible by the invention. The hot sodium comes from a heat exchanger 31 which is usually placed in a lower position than the heat exchanger and returns to a pump 32 after cooling, said pump being usually placed at the same level as the top of the heat exchanger. The reduction in length of piping is clearly demonstrated in this figure.

In the case of FIG. 3, the heat exchanger is in fact the steam generator of a nuclear power station in which a breeder reactor is cooled by liquid sodium or another liquid alkali metal. During operation of the heat exchanger, heat is transferred from the hot sodium which is cooled to the water which vaporizes.

Said steam generator (shown in FIG. 3) is made up of one or a number of units in accordance with the invention, these units being disposed in parallel at different points of its circuit in order to ensure heating and vaporization of the water, superheating and in some cases resuperheating (not shown in the drawings).

What we claim is:

l. A heat-exchanger unit comprising a tube bundle, an inner sleeve surrounding said bundle, openings located at the ends of the inner sleeve for admission and discharge of a first fluid into and from said bundle, an outer shell for the heat-exchanger unit spaced from said inner sleeve, a jacket on said inner sleeve extending downwardly between said sleeve and said outer shell a transverse partition-wall between said jacket and said shell, two annular spaces consisting of an upper and lower space between said wall and said jacket and said shell, external ducts opening into said spaces for the admission and discharge of a second fluid, and said ducts opening immediately adjacent to said partition-wall whereby minimum differential ex pansion under both steady-state and transient flow conditions occurs between said outer shell and the tubes of said bundle.

2. A heat-exchanger unit in accordance with claim 1, said transverse partition-wall including a supporting ring fixed on said jacket, two sets of radial fins disposed on each side of said partition-wall within said annular spaces preventing circulation of the second fluid in the vicinity of said partition-wall, whereby said external ducts for the admission and discharge of the second fluid are insulated hydraulically and thermally both with respect to each other and with respect to said tube bundle.

3. A heat-exchanger unit in accordance with claim 2,

'one of said sets of radial tins being rigidly fixed to said mini ducts of each unit reducing the length of the piping for the second fluid and connecting the units for vaporization, superheating and resuperheating. 

1. A heat-exchanger unit comprising a tube bundle, an inner sleeve surrounding said bundle, openings located at the ends of the inner sleeve for admission and discharge of a first fluid into and from said bundle, an outer shell for the heat-exchanger unit spaced from said inner sleeve, a jacket on said inner sleeve extending downwardly between said sleeve and said outer shell a transverse partition-wall between said jacket and said shell, two annular spaces consisting of an upper and lower space between said wall and said jacket and said shell, external ducts opening into said spaces for the admission and discharge of a second fluid, and said ducts opening immediately adjacent to said partition-wall whereby minimum differential expansion under both steady-state and transient flow conditions occurs between said outer shell and the tubes of said bundle.
 2. A heat-exchanger unit in accordance with claim 1, said transverse partition-wall including a supporting ring fixed on said jacket, two sets of radial fins disposed on each side of said partition-wall within said annular spaces preventing circulation of the second fluid in the vicinity of said partition-wall, whereby said external ducts for the admission and discharge of the second fluid are insulated hydraulically and thermally both with respect to each other and with respect to said tube bundle.
 3. A heat-exchanger unit in accordance with claim 2, one of said sets of radial fins being rigidly fixed to said inner sleeve.
 4. A heat-exchanger unit in accordance with claim 2, one of said sets of radial fins being rigidly fixed to said outer shell.
 5. A heat-exchanger unit in accordance with claim 2, said supporting ring resting on an internal shoulder of said outer shell.
 6. A group of interconnected units in accordance with claim 1, said group being a steam generator, the first unit providing heating and vaporization, the second unit providing superheating, the thirD unit providing resuperheating, the arrangement of said inlet and outlet ducts of each unit reducing the length of the piping for the second fluid and connecting the units for vaporization, superheating and resuperheating. 